Printing machines, particularly sheet-fed offset printing machines, increasingly utilize partially or completely automated printing machine plate changers. During a plate change process, a used printing plate in a printing unit is removed from a plate cylinder and a new printing plate required for the next print job is forwarded onto the plate cylinder. In offset printing machines, where printing units are constructed in series, the printing plate changers are included either as separate devices, upstream or downstream from the printing unit, or they are integrated into the printing unit.
In conventional printing machines, these automated printing plate changers comprise the delivery means for conveying a new printing plate onto the plate cylinder from a storage chamber or magazine, as well as the appropriate means for removing the used printing plate from the plate cylinder and conveying the plate into the storage chamber or magazine. In addition, the automated printing plate changers are coupled to a control system which allows the plate change process in each printing unit to be executed in a pre-programmed manner. The control system, in addition to controlling the conveyance of the printing plate, controls the positioning of the individual printing units and the printing machine in order to correctly align the print cylinders. The control system is further connected to actuators necessary for clamping and tensioning the printing plates located on the plate cylinder. Through the use of interrogatable position sensors, progress of the automated printing plate change process is monitored by the control system along with successively executing the working steps necessary to complete the change process.
Disclosed in U.S. Pat. No. 5,111,744 (and corresponding German Patent DE 3 940 796 C2) is a method and a device for automatically changing printing plates in a printing machine. This device comprises the components described above, such as the actuators for clamping and tensioning the printing plate located on the printing cylinder, the conveying means for conveying the printing plate to and from the printing cylinder, a control system coupled to the printing machine used to position the plate cylinders, and position sensors for controlling the working steps required to complete the plate change process.
German Patent DE 9 411 254 U1 discloses a monitoring device for automated printing plate changers. This device is a sensor coupled to the control system of the printing machine or the printing plate changing system. The device operates by detecting the rotation of the back-pressure roller in conjunction with the transport roller.
Disclosed in U.S. Pat. No. 5,634,406 (and corresponding German Patent DE 4 439 632 A1) is a method for automatically feeding a printing plate to the plate cylinder of a printing machine. According to the method, the printing plate is advanced by a plate conveyor towards a clamping rail on the plate cylinder. Position sensors are used to determine if the printing plate is properly aligned at two independent sites. If the printing plate is misaligned at either site or both sites, the printing plate is released and the process is repeated. Once the printing plate is aligned, the plate is finally mounted on the plate cylinder. A method and device for controlling the required sequence of steps in this method is disclosed in U.S. Pat. No. 5,479,859 (and corresponding German Patent DE 4 338 664 C2).
In general, sheet-fed offset printing machines, particularly sheet-fed offset printing machines which utilize printing plate changers and methods as described above, include a human-machine interface or control console. The human-machine interface, which is used to input data, control the system, and monitor the plate change process, is comprised of an input device and a display device in the form of a monitor. Through the human-machine interface, it is possible to display signals and measured values of the current print job and at the same time enter data and settings required for the next print job.
The prior art listed above describes the methods and devices for controlling an automated printing plate change process. These methods and devices relate to the change process as a whole or describe specific individual steps of the change process. The prior art, however, does not allow the operator to view, through a visual display device, the sequence of operations executed during the automated printing plate change process. Nor does the prior art detect and display where in the printing machine, and in which printing unit in particular, a fault occurred during the plate change process. The prior art further does not identify what type of fault occurred during the plate change process. The prior art simply monitors only one part of a very complex change process which involves a large number of individual steps.